Valve uses VAC and has always used VAC, it is incredibly unlikely they would ever use a different anti-cheat imo.
What OP is worrying about is Valve reworking VAC into a kernel anticheat. Right now VAC is a usermode anticheat based around detecting signatures of anticheat programs/signs of tampering with the game(sometimes overdoing it as AMD users were flagged as cheaters when AntiLag+ was released with a driver update, though those bans were reversed).
I believe the same spyware is coming to LoL and their other games as well at some point, if it hasn't already.
They already added it to League, but only to the Windows version. The macOS client uses "an alternative version"(though I presume once Apple drops x86 emulation from macOS, the mac client will die with it), and Linux users that used Wine to play League were thrown under the bus
Steam Deck is a Linux device so I don't know how accurate the idea that Valve will be quick to throw it overboard is. Non-Steam Deck users are a side effect and not a goal, so, sure, no one cares about them specifically but they can't get fucked without Valve fucking themselves, too.
That said, with the leaderless chaos that is Valve's employees, that the left hand didn't know what the right hand is doing wouldn't be too much of a stretch.
What OP is worrying about is Valve reworking VAC into a kernel anticheat. Right now VAC is a usermode anticheat based around detecting signatures of anticheat programs/signs of tampering with the game(sometimes overdoing it as AMD users were flagged as cheaters when AntiLag+ was released with a driver update, though those bans were reversed).
They already added it to League, but only to the Windows version. The macOS client uses "an alternative version"(though I presume once Apple drops x86 emulation from macOS, the mac client will die with it), and Linux users that used Wine to play League were thrown under the bus
Steam Deck is a Linux device so I don't know how accurate the idea that Valve will be quick to throw it overboard is. Non-Steam Deck users are a side effect and not a goal, so, sure, no one cares about them specifically but they can't get fucked without Valve fucking themselves, too.
That said, with the leaderless chaos that is Valve's employees, that the left hand didn't know what the right hand is doing wouldn't be too much of a stretch.